org.apache.tools.ant

Class IntrospectionHelper

Implemented Interfaces:
BuildListener, EventListener

public final class IntrospectionHelper
extends java.lang.Object
implements BuildListener

Helper class that collects the methods a task or nested element holds to set attributes, create nested elements or hold PCDATA elements. The class is final as it has a private constructor.

Nested Class Summary

static class
IntrospectionHelper.Creator
creator - allows use of create/store external to IntrospectionHelper.

Method Summary

void
addText(Project project, Object element, String text)
Adds PCDATA to an element, using the element's void addText(String) method, if it has one.
void
buildFinished(BuildEvent event)
Clears all storage used by this class, including the static cache of helpers.
void
buildStarted(BuildEvent event)
Empty implementation to satisfy the BuildListener interface.
Object
createElement(Project project, Object parent, String elementName)
Deprecated. This is not a namespace aware method.
Class
getAttributeType(String attributeName)
Returns the type of a named attribute.
Enumeration
getAttributes()
Returns an enumeration of the names of the attributes supported by the introspected class.
IntrospectionHelper.Creator
getElementCreator(Project project, String parentUri, Object parent, String elementName, UnknownElement ue)
returns an object that creates and stores an object for an element of a parent.
protected String
getElementName(Project project, Object element)
Returns a description of the type of the given element in relation to a given project.
Class
getElementType(String elementName)
Returns the type of a named nested element.
static IntrospectionHelper
getHelper(Class c)
Returns a helper for the given class, either from the cache or by creating a new instance.
static IntrospectionHelper
getHelper(Project p, Class c)
Returns a helper for the given class, either from the cache or by creating a new instance.
Enumeration
getNestedElements()
Returns an enumeration of the names of the nested elements supported by the introspected class.
void
messageLogged(BuildEvent event)
Empty implementation to satisfy the BuildListener interface.
void
setAttribute(Project p, Object element, String attributeName, String value)
Sets the named attribute in the given element, which is part of the given project.
void
storeElement(Project project, Object parent, Object child, String elementName)
Stores a named nested element using a storage method determined by the initial introspection.
boolean
supportsCharacters()
Returns whether or not the introspected class supports PCDATA.
boolean
supportsNestedElement(String elementName)
Indicate if this element supports a nested element of the given name.
boolean
supportsNestedElement(String parentUri, String elementName)
Indicate if this element supports a nested element of the given name.
void
targetFinished(BuildEvent event)
Empty implementation to satisfy the BuildListener interface.
void
targetStarted(BuildEvent event)
Empty implementation to satisfy the BuildListener interface.
void
taskFinished(BuildEvent event)
Empty implementation to satisfy the BuildListener interface.
void
taskStarted(BuildEvent event)
Empty implementation to satisfy the BuildListener interface.
void
throwNotSupported(Project project, Object parent, String elementName)
Utility method to throw a NotSupported exception

Method Details

addText

public void addText(Project project,
                    Object element,
                    String text)
            throws BuildException
Adds PCDATA to an element, using the element's void addText(String) method, if it has one. If no such method is present, a BuildException is thrown if the given text contains non-whitespace.

Parameters:
project - The project which the element is part of. Must not be null.
element - The element to add the text to. Must not be null.
text - The text to add. Must not be null.

Throws:
BuildException - if non-whitespace text is provided and no method is available to handle it, or if the handling method fails.


buildFinished

public void buildFinished(BuildEvent event)
Clears all storage used by this class, including the static cache of helpers.
Specified by:
buildFinished in interface BuildListener

Parameters:
event - Ignored in this implementation.


buildStarted

public void buildStarted(BuildEvent event)
Empty implementation to satisfy the BuildListener interface.
Specified by:
buildStarted in interface BuildListener

Parameters:
event - Ignored in this implementation.


createElement

public Object createElement(Project project,
                            Object parent,
                            String elementName)
            throws BuildException

Deprecated. This is not a namespace aware method.

Creates a named nested element. Depending on the results of the initial introspection, either a method in the given parent instance or a simple no-arg constructor is used to create an instance of the specified element type.

Parameters:
project - Project to which the parent object belongs. Must not be null. If the resulting object is an instance of ProjectComponent, its Project reference is set to this parameter value.
parent - Parent object used to create the instance. Must not be null.
elementName - Name of the element to create an instance of. Must not be null.

Returns:
an instance of the specified element type

Throws:
BuildException - if no method is available to create the element instance, or if the creating method fails.


getAttributeType

public Class getAttributeType(String attributeName)
            throws BuildException
Returns the type of a named attribute.

Parameters:
attributeName - The name of the attribute to find the type of. Must not be null.

Returns:
the type of the attribute with the specified name. This will never be null.

Throws:
BuildException - if the introspected class does not support the named attribute.


getAttributes

public Enumeration getAttributes()
Returns an enumeration of the names of the attributes supported by the introspected class.

Returns:
an enumeration of the names of the attributes supported by the introspected class.


getElementCreator

public IntrospectionHelper.Creator getElementCreator(Project project,
                                                     String parentUri,
                                                     Object parent,
                                                     String elementName,
                                                     UnknownElement ue)
returns an object that creates and stores an object for an element of a parent.

Parameters:
project - Project to which the parent object belongs.
parentUri - The namespace uri of the parent object.
parent - Parent object used to create the creator object to create and store and instance of a subelement.
elementName - Name of the element to create an instance of.
ue - The unknown element associated with the element.

Returns:
a creator object to create and store the element instance.


getElementName

protected String getElementName(Project project,
                                Object element)
Returns a description of the type of the given element in relation to a given project. This is used for logging purposes when the element is asked to cope with some data it has no way of handling.

Parameters:
project - The project the element is defined in. Must not be null.
element - The element to describe. Must not be null.

Returns:
a description of the element type


getElementType

public Class getElementType(String elementName)
            throws BuildException
Returns the type of a named nested element.

Parameters:
elementName - The name of the element to find the type of. Must not be null.

Returns:
the type of the nested element with the specified name. This will never be null.

Throws:
BuildException - if the introspected class does not support the named nested element.


getHelper

public static IntrospectionHelper getHelper(Class c)
Returns a helper for the given class, either from the cache or by creating a new instance.

Parameters:
c - The class for which a helper is required. Must not be null.

Returns:
a helper for the specified class


getHelper

public static IntrospectionHelper getHelper(Project p,
                                            Class c)
Returns a helper for the given class, either from the cache or by creating a new instance. The method will make sure the helper will be cleaned up at the end of the project, and only one instance will be created for each class.

Parameters:
p - the project instance
c - The class for which a helper is required. Must not be null.

Returns:
a helper for the specified class


getNestedElements

public Enumeration getNestedElements()
Returns an enumeration of the names of the nested elements supported by the introspected class.

Returns:
an enumeration of the names of the nested elements supported by the introspected class.


messageLogged

public void messageLogged(BuildEvent event)
Empty implementation to satisfy the BuildListener interface.
Specified by:
messageLogged in interface BuildListener

Parameters:
event - Ignored in this implementation.


setAttribute

public void setAttribute(Project p,
                         Object element,
                         String attributeName,
                         String value)
            throws BuildException
Sets the named attribute in the given element, which is part of the given project.

Parameters:
p - The project containing the element. This is used when files need to be resolved. Must not be null.
element - The element to set the attribute in. Must not be null.
attributeName - The name of the attribute to set. Must not be null.
value - The value to set the attribute to. This may be interpreted or converted to the necessary type if the setter method doesn't just take a string. Must not be null.

Throws:
BuildException - if the introspected class doesn't support the given attribute, or if the setting method fails.


storeElement

public void storeElement(Project project,
                         Object parent,
                         Object child,
                         String elementName)
            throws BuildException
Stores a named nested element using a storage method determined by the initial introspection. If no appropriate storage method is available, this method returns immediately.

Parameters:
project - Ignored in this implementation. May be null.
parent - Parent instance to store the child in. Must not be null.
child - Child instance to store in the parent. Should not be null.
elementName - Name of the child element to store. May be null, in which case this method returns immediately.

Throws:
BuildException - if the storage method fails.


supportsCharacters

public boolean supportsCharacters()
Returns whether or not the introspected class supports PCDATA.

Returns:
whether or not the introspected class supports PCDATA.


supportsNestedElement

public boolean supportsNestedElement(String elementName)
Indicate if this element supports a nested element of the given name.

Parameters:
elementName - the name of the nested element being checked

Returns:
true if the given nested element is supported


supportsNestedElement

public boolean supportsNestedElement(String parentUri,
                                     String elementName)
Indicate if this element supports a nested element of the given name.

Parameters:
parentUri - the uri of the parent
elementName - the name of the nested element being checked

Returns:
true if the given nested element is supported


targetFinished

public void targetFinished(BuildEvent event)
Empty implementation to satisfy the BuildListener interface.
Specified by:
targetFinished in interface BuildListener

Parameters:
event - Ignored in this implementation.


targetStarted

public void targetStarted(BuildEvent event)
Empty implementation to satisfy the BuildListener interface.
Specified by:
targetStarted in interface BuildListener

Parameters:
event - Ignored in this implementation.


taskFinished

public void taskFinished(BuildEvent event)
Empty implementation to satisfy the BuildListener interface.
Specified by:
taskFinished in interface BuildListener

Parameters:
event - Ignored in this implementation.


taskStarted

public void taskStarted(BuildEvent event)
Empty implementation to satisfy the BuildListener interface.
Specified by:
taskStarted in interface BuildListener

Parameters:
event - Ignored in this implementation.


throwNotSupported

public void throwNotSupported(Project project,
                              Object parent,
                              String elementName)
Utility method to throw a NotSupported exception

Parameters:
project - the Project instance.
parent - the object which doesn't support a requested element
elementName - the name of the Element which is trying to be created.


Copyright B) 2000-2005 Apache Software Foundation. All Rights Reserved.